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of which cannot be increased much beyond its normal rate, it will be advisable to place gas-burners in the main ventilating-chimney, to be lighted only when a temporary overcrowding or the fear of epidemics renders their use necessary.

The number of burners and their consumption of gas will be calcu lated on the approximate basis of 500 cubic feet of air removed to each cubic feet of gas burned.

This auxiliary means is not economical, and should only be employed in exceptional circumstances.

ASYLUMS.

95. Asylums, designed for the old, insane, or infirm, do not require, for salubrity, as much ventilation as hospitals.

A renewal of air at the rate of 1,000 cubic feet of air an hour for each individual during the day and 1,400 cubic feet at night will be sufficient. It will then only be necessary to adopt the plans and the dimensions which have been given in detail for hospitals.

For heating during the winter, if the rooms are not very large, ventilating fire-places should be used, which will also secure the renewal of air. But for spring, summer, and autumn, it will be necessary to have recourse, for the removal of foul air, to the use of a ventilating-chimney and the arrangements before mentioned.

CHURCHES.

96. The great size of churches, the constant opening of their doors, the extent of glazed windows-always imperfectly closed-the openings in the vaults for the suspension of lamps or draperies and for the passage of bell-ropes, seem in general to render unnecessary the adoption of special arrangements for the admission and the removal of air, and reduce for the winter the question to that of warming.

For the churches of large cities, frequented at many hours of the day, it seems economical to keep up an active fire, constantly, day and night. Either hot-air heaters, with chambers for the admission of cold air, or bot-water heaters, may be used. The first suit more particularly the small churches, where a single heater, placed about the middle of the building, will suffice. The second, which carry heat to great distances, and give, besides, a more equable temperature, should be preferred for large churches. They have, in addition, the advantage of being readily adapted to ventilate certain attached places, such as catechising-rooms, where the air is constantly vitiated by the presence of many children. What is most necessary to warm in churches is the floor itself. For this purpose it would be well to make the hot-water pipes branch out under many parts of the floor, and limit the number of fresh air openings. This arrangement is similar to that of which traces are found in Roman constructions.

The air to be warmed by the heaters is taken from outside. A sufficient number of pipes in the aisles and passages admit the air through numerous openings placed in the vertical faces of the walls, or in the bases of the columns, a little above the floor, and not at the floor-level, as is often wrongly done.

During the summer season, the interior of churches, strongly heated during the day by the action of the sun on the roof and through the large windows, is often uncomfortable to stay in, especially in the morning. It would be easy to avoid this trouble by arranging a number of windows to be opened at night, in order to admit the fresh air, and to be shut in the morning. The interior, thus cooled during the night, would be less warmed during the day.

These precautions, much neglected in France, where the heat of summer seldom proves unpleasant, are regularly carried out in Rome, where it lasts a long time. A rule of the custodians of St. Peter's requires that the windows of the upper galleries be opened every evening in summer and closed every morning.

What precedes only applies to ordinary churches; but in the case of chapels or subterranean churches, the interior height of which is very limited and which are often occupied by a large number of worshippers and fully lighted up, it becomes necessary to secure the renewal of air and the removal of the hot gases arising from the lights. The plans proposed in § 64 for night drawing-schools should then be adopted, producing a renewal of air at least five or six times an hour.

In churches where great ceremonies require the use of large canopies, preventing the circulation of the air, and in which a great number of candles occasion often an extraordinary elevation of temperature, it is very important that the construction should allow of forming, in the upper or lateral portion, as many openings as possible in order to allow the external air to flow in with a velocity which will be less the greater the number of these openings and the more uniformly they are distributed. In this way will be avoided the at times unendurable currents of air produced by the doors and the elevation of temperature.

In winter, at the time of thaws after great cold, especially in the north, there is produced on the walls, and still more on the ceiling, a condensation of vapor, which often produces a sort of rain that affects the paintings. In such cases, it would be well to carry the warm air supplied by the heaters at about from 140° to 175° directly to the upper part of these edifices at the springing of the arches, in order to keep the vapor arising from the people in the lower portions of the church from condensing.

RAILROAD-STATIONS.

97. As an example of cases where it is proper to act contrary to the general rules given before, we will specify the methods to be adopted for

*In a great funeral-ceremony at Notre-Dame, Paris, the heat was such that the waxtapers began to melt.

railroad-stations, for markets, and for large buildings such as those for exhibitions.

These immense buildings, covered in most cases with glass roofs, which often leave only a very small space for the escape of the smoke and steam of the locomotives and of the hot air in summer, sometimes become unendurable for the employés. One end of the building is almost entirely shut in by the gable-wall containing the main entrance; the other usually has an opening only high enough for the passage of the locomotive; the sides occupied on the ground-level by waiting-rooms, &c., and on the second and third floors by offices, do not allow the air to have access to the building, and in the hot season the temperature rises near the ground-level to 104°, 113° and even 1220, as has been observed at the stations of the Lyons, Eastern, and Strasburg railroads.

In order to remedy this state of things, it is necessary to raise the skylights on the roof, not only because they are too low, but because in winter they cool the smoke and partially condense the escape-steam of the engine, and thus interfere with its removal.

Instead of placing the sky-lights at the ridge of the roof, it would seem better to place them near the eaves, making them, as at present, equal to one-fourth or one-third the total surface.

The ventilating-opening should be formed by two vertical walls of sheet-iron about 10 feet high, leaving between them a passage extending the whole length of the roof, the breadth of which should be calculated so as to renew the air of the station at least twice or three times an hour, on the supposition that the heat of the sun in summer is sufficient to produce, in a sheet-iron chimney 10 feet high, a velocity of from 1 to 2 feet a second.

To replace regularly the air removed without producing unpleasant currents at the end-openings of the station, it is necessary to increase the number of openings for admission of air, and place them as uniformly as possible throughout the extent of the station, and also to make large doorways in the two ends of the building. The total area of the freshair openings should be such that, with a velocity of at most 16 to 20 inches a second, a volume of air may enter into the station equal to twice or three times its cubical capacity.

98. Sprinkling of roofs.-In addition to the preceding arrangements, proper for all seasons, it would be well, in hot weather, to keep up a constant sprinkling of the roof, commencing at seven or eight o'clock in the morning and lasting till five o'clock in the evening, using about 44 cubic feet of water an hour to every 100 square feet of roof-surface. This sprinkling, which will be sufficient to prevent the heating of the roof by the action of the solar rays, added to the continued aeration, will maintain the temperature within convenient limits during the hot

season.

99. Example. The Orleans station is 348 feet long, 92 feet wide, 26 feet high at the springing-line, and 44 feet to the ridge. Its cubical content is about 1,130,000 cubic feet.

3 × 1130000 To renew the air three times an hour, it should carry off- 3600 =942 cubic feet a second. The velocity which the solar heat may give to the escaping air being estimated at but 1ğ feet a second, the sectional area of the ventilating-space should be 574 square feet; and if the ventilatingpassage is carried the whole length of the roof, which is 328 feet, it would suffice to make it 1 foot 9 inches wide. But as the part where there is most smoke and steam is usually near the end at which the trains leave, instead of making the ventilating-opening extend the whole length of the station, it would be better to give it greater breadth and less length, still retaining the same sectional area.

COURTS AND COVERED MARKETS.

100. Similar arrangements should be adopted in the case of courts and for all covered markets.

In the latter, where blinds are usually placed in the windows, the introduction of air is easily provided for, and it is particularly the removal of foul air that requires attention.

GLASS ROOFS AND CEILINGS.

101. Influence of glazed roofs and ceilings during the winter.-If in the summer season the glazed roofs of stations and covered courts present the inconvenience of producing a heating effect, which it is necessary to overcome, in winter they have the contrary defect, which often leads to very disagreeable results.

The conductibility of thin glass then leads to a considerable cooling of the interior layers of air in contact with the glass; this air, becoming denser than that below, descends, and is constantly replaced by more, which is likewise cooled, and by this continued movement the rooms thus covered become very difficult to warm.

To these troubles is added that of the motion of the cold air, which naturally flows toward the chimneys, or the discharge-openings, if there are any, so that the occupants feel a descending current of cold air, the more unpleasant the nearer they are to the chimney or the dischargeopenings.

If the glass roof is simple, and has, as is almost inevitably the case, joints, through which the external air-much colder than that in contact with the internal surface-penetrates into the room, the effects which have been mentioned become more sensible and disagreeable. There is also the danger that water will enter during rain-storms.

It is, then, necessary in occupied buildings, when similar plans are adopted for lighting, to place under the roof a glass ceiling with as few joints as possible, and in the loft thus formed and limited above and below, to provide heating arrangements which will prevent the cooling of the ceiling, and thus to avoid the cold air currents which have just been referred to.

102. Observations at Château de Ferrières.-The most striking example of these effects which I have had occasion to observe is presented by the great reception-hall of the Château de Ferrières, and it has furnished me with some facts which enable me to determine the amount of heat which such glass roofs may transmit, and, consequently, to determine approximately the methods of heating to be employed to prevent this cooling.

The main reception-room of the Château de Ferrières, called the Hall, is 75 feet long and 40 feet wide, or 3,000 square feet in area.

It is completely surrounded by other reception-rooms, corridors, vestibules, &c. By means of heaters, all these are comfortably warmed, as well as the reception-room, which has no side-windows, but is lighted by a glass ceiling with a surface of 1,635 square feet, covered by a glass roof in seven sections, having together 2,459 square feet of cooling surface.

A large fire-place, in the form of a monument, placed on one of the long sides of the room, completes its system of heating.

When in winter the space between the glass roof and ceiling is not warmed during the day, the effects previously mentioned become the most unpleasant. The considerable draught of air produced by the fireplace draws to it the air cooled by contact with the ceiling; and the vicinity of this fire-place, to which persons are naturally drawn by a bright fire, becomes unendurable.

At night, the room is lighted up by 1,000 gas-burners above the ceil ing, which consume 3,500 cubic feet of gas an hour; there being then about one burner to every three square feet of floor-surface in the room. The heat given out by this abundant combustion more than suffices to prevent the cooling of the air of the room and the unpleasant effects which would result from it.

To obtain at least to a certain degree the same result during the day, it has been found necessary to keep up coke-fires in four cast-iron stoves, placed in the roof-space, in order to maintain there a temperature higher than that of the room.

Observations made on the consumption of coke during the day and of gas at night, as well as upon the internal and external temperatures, enable us to calculate at least approximately the amount of heat required in the space between the glass roof and ceiling in order to prevent the unpleasant cooling effect.

For this purpose, calling

C the number of units of heat which can pass in an hour through a pane of glass having the surface S;

T the temperature of the air on the warmer side;

T' that of the air on the colder side;

K a constant co-efficient, representing the number of units of heat to a square foot of glass surface, and to a degree of difference of temperature between the two faces:

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